A tattoo is a design created on the skin, or sometimes other tissue, by the injection of pigment into the dermal layer, so it is visible through the surface. The most common type of tattooing device is a vibrating needle controlled by the operator as a hand-held tool that vibrates rapidly, ordinarily between 50-3,000 times per minute, to inject non-water soluble pigment in the desired pattern. If the injection is too deep, it may not be easily visible through the surface or may look blurred. If it is too superficial, it may not be held in proper position and may migrate to produce a blurred image or be gradually removed to produce a faded image as the dermis is recycled. Usually, the pattern is first outlined free-hand with a stencil in dark colored ink, and then the colors are filled in. Ordinarily the tattooing needle injects a single color at a time, and repeated applications are necessary to produce a multi-colored pattern. Tattoo designs may be small and localized, or may be any size up to covering most or the entire skin surface.
In some cultures and in more primitive times, the pigment is placed on the skin and pushed in by needles or other relatively sharp objects held by hand, or pulled into the skin on thread that is passed into and out of the surface on a curved needle.
Some attempts have been made to automate placing of temporary decorations or tattoos on a body surface. For example, U.S. Pat. No. 6,341,831 to Weber et al. discloses a skin decoration apparatus and method for placing temporary multi-colored designs using Wirejet™ technology. The decoration is produced by a print head comprising Wirejet™ nozzles, which spray biocompatible inks or dyes onto the skin and last for at least several weeks. The Wirejet™ may be connected to a scanning mechanism to scan in one, two, or three directions. The decorations can be applied to contoured skin surfaces following flattening against a screen of intersecting wires, by robotic arm, or using z-axis technology. A computer stores the desired design and controls the firing of the Wirejet™ to produce the desired decoration.
Placing of permanent conventional tattoos generally involves using a needle that is controlled by the tattoo artist, it is inexact, tedious, time consuming, laborious, and consequently expensive. Similarly, despite certain advancements in a laser tattoo removal technology, conventional tattoo removal is done manually by a person, requires multiple sessions and suffers from many shortcomings.